1. Field of the Invention
The present invention relates to a display panel driver for driving a display panel and, in particular, to a display panel driver for receiving video signals in accordance with a low-voltage differential method.
2. Description of the Related Art
An interface of a conventional liquid crystal display apparatus transmits respective bits of RGB video signals, horizontal synchronous signals, vertical synchronous signals and data enable signals in parallel at an amplitude voltage of 5 V or +3.3 V. However, as the resolution of recent liquid display panels has increased, the number of interfaces and the frequency of transmitted signals has increased. As a result, problems including electromagnetic interface (EMI) noise may occur. The number of interfaces has increased because, in order to transfer 24-bit data, for example, 51 signal lines including 48 (=24×2) signal lines and signal lines for control signals are required. If GND lines are included therein, about 60 signal lines are required in total. Generally speaking, at the amplitude voltage of +5 V or +3.3 V, 30 MHz is the limit of the transmitting frequency. Thus, in order to reduce the number of interfaces and to protect against EMI, a low-voltage differential signaling method such as Low Voltage Differential Signaling (LVDS) has been proposed and has become commercially practical. In LVDS, the video signals, synchronous signals and data enable signals having been transmitted in parallel are serialized and transferred at a higher speed than the transfer rate of the original video signals and at a lower voltage amplitude.
A liquid crystal display apparatus using the conventional LVDS as an interface includes an LVDS receiver IC, a timing controller IC, multiple source driver ICs, and multiple gate driver ICs. The LVDS receiver IC receives LVDS signals including video signal data and synchronous signal data and retrieves video signals, synchronous signals, clock signals and data enable signals from the LVDS signals. Then, the LVDS receiver IC converts the video signals, synchronous signals, clock signals and data enable signals to TTL/CMOS signals. The timing controller IC generates display signals and display control signals from the TTL/CMOS signals. The multiple source driver ICs generate and output drive signals for driving signal lines of the liquid crystal panel based on the display signals and the display control signals. The multiple gate driver ICs generate and output drive signals for driving scan lines of the liquid crystal panel based on the display control signals. However, in this case, the TTL/CMOS signals are generally transmitted through about 24 transmission lines connecting from the timing controller IC to the source driver ICS. Therefore, an area for the wiring is required, and EMI noise is radiated from the transmission lines, both of which are problems.
In order to solve these problems, a liquid crystal display apparatus has been proposed (as disclosed in Japanese Unexamined Patent Application Publication No. 2000-152130) which adopts a low-voltage differential signaling method for the interface between a timing controller IC and source driver ICs.
However, in order to increase the resolution of a liquid crystal panel and the transfer speed of transmitted data between the timing controller and the signal line driver, the number of transmission lines must be increased because of the upper limit of the transfer frequency of the transmission lines or the operational frequency of the transmit/receive circuit. Therefore, the problem of increased EMI noise due to the increases in size of the wiring space and in the number of wires becomes more significant. In addition, currently, a further reduction in the size of a non-display area surrounding a liquid crystal panel of a liquid crystal display apparatus is in demand. Thus, the existence of the wiring space surrounding the liquid crystal panel and a connection substrate around the liquid crystal panel becomes a problem.